How can I linear increase to Location Value
You only need two keyframes to animate a value with a constant linear variance.

By default an fcurve uses a constant extrapolation, that is it stays at the last animated value. You can change this in the Graph Editor or the Dopesheet in the Channel->Extrapolation Mode menu or &#8679; ShiftE.



If you want it to stop after a certain time, you can go to that frame and insert a new keyframe, then reset the extrapolation back to constant.